JPH0661952A - Multi-path simulator - Google Patents

Abstract

PURPOSE:To provide a multi-path simulator which can omit a delay circuit of high frequency and also can omit the matching between the oscillation phase and the frequency. CONSTITUTION:A multi-path simulator is provided with signal generating means 1 which generates a modulated wave signal, etc., a phase difference generating means 2 which calculates the difference between the modulated signal converted into a digital signal and the modulated signal delayed by a prescribed time, integrates the difference, and externally adds the phase difference of the carrier between a direct wave and a reflected wave to the integrated value to generate a phase difference, and a high frequency phase control means 3 which produces the cosine and sine wave signals based on the phase difference calcilated by the means 2, converts these wave signals into the analog signals, mixes the modulated wave signal with the sine wave analog signal, mixes a 90 deg. phase shifted modulated wave signal with the cosine wave analog signal, adds these mixed signals together to synthesize the phase difference and the modulated wave, and produces a reflected wave signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multipath simulator for simulating multipath, and more particularly to an audio signal processing which does not require a high frequency delay circuit and does not require oscillation phase and frequency matching.

[0002]

2. Description of the Related Art An audio device mounted on a vehicle or the like is affected by multipath while traveling, and therefore must be designed in consideration of this influence. However, actually running a vehicle to test the effects of multipath involves a great deal of work, so a multipath simulator that simulates the reflected wave of a building or the like against the direct wave and synthesizes the direct wave and the reflected wave is an audio system. Used for testing equipment. Technologies in such fields include those described below.

FIG. 2 is a diagram showing a conventional multipath simulator. The multipath simulator in the case of FM modulation shown in the figure first comprises an oscillator 100 for generating a carrier wave of radio frequency. The FM modulator 101 connected to the oscillator 100 FM-modulates the carrier of the oscillator 100 by the modulation input. The demultiplexer 102 connected to the FM modulator 101 demultiplexes the FM modulated signal into two in order to form a direct wave and a reflected wave. A delay circuit 103 connected to the demultiplexer 102 delays one output of the demultiplexer by a time period in which a radio wave propagates a distance of 10 m to several km, for example. The delay circuit 103 is usually composed of a crystal filter, and the delay characteristic of the crystal filter is used. The variable phase shifter 104 connected to the delay circuit 103 changes the phase of the signal delayed by the delay circuit 103, and the level shifter 105 connected to the variable phase shifter 104 changes the phase by the variable phase shifter 104. Change the level of the signal. The combining unit 106 connected to the level variable unit 105 combines the signal whose level has been changed by the level variable unit 105 and the other signal of the demultiplexer 102 to form a multipath signal. Was used for testing audio equipment.

[0004]

However, the crystal filter used in the delay circuit 103 in the conventional multipath simulator has poor phase stability, that is, its characteristics change greatly depending on temperature, and therefore the phase is frequently calibrated. There was a problem that it was necessary. Moreover, there is no alternative to the crystal filter with good phase stability, and the cost is high. Therefore, in view of the above problems, it is an object of the present invention to provide a multipath simulator that does not require a high-frequency delay circuit and does not require phase and frequency matching of oscillation due to temperature fluctuations.

[0005]

In order to solve the above-mentioned problems, the present invention provides a multipath simulator for simulating and combining a direct wave and a reflected wave, a signal generating means, a phase difference forming means, and a high frequency phase control. Provide means. The signal generating means modulates a carrier signal with a modulation signal to form the direct wave and the reflected wave to form a modulated wave signal.

The phase difference forming means takes a difference between the modulated signal converted into a digital signal and a delayed modulated signal obtained by delaying this signal by a predetermined time, integrates the difference, and directly obtains the integrated value as a direct external wave. The phase difference between the reflected wave and the carrier wave is added to form the phase difference. The high frequency phase control means forms a cosine wave signal and a sine wave signal from the phase difference, converts them into an analog signal, mixes the modulated wave signal and the sine wave analog signal, and shifts the phase by 90 degrees. Wave signal and the cosine wave analog signal are mixed, these mixed signals are added, and the phase difference and the modulated wave signal are combined to form a reflected wave signal. It is used to adjust the attenuation with the modulated wave signal as a signal and synthesize a multipath signal.

[0007]

According to the multipath simulator of the present invention, the carrier wave signal is modulated by the modulation signal in the signal generating means to form a modulated wave signal. In the phase difference forming means, a difference between the modulated signal converted into a digital signal and a delayed modulated signal obtained by delaying this signal by a predetermined time is taken, the difference is integrated, and a direct wave and a reflected wave are externally added to the integrated value. And the phase difference of the carrier wave is added to form the phase difference between the direct wave and the reflected wave. Therefore, the formation of a phase difference that simulates the delay between the direct wave and the reflected wave, and the phase difference of the carrier wave between the direct wave and the reflected wave can be obtained by digital signal processing in the audio frequency range. The temperature stability is significantly improved. The high frequency phase control means forms a cosine wave signal and a sine wave signal from the phase difference, converts them into an analog signal, mixes the modulated wave signal and the sine wave analog signal, and shifts the phase by 90 degrees. A signal and the cosine wave analog signal are mixed, these mixed signals are added, and the phase difference and the modulated wave signal are combined to form a reflected wave signal. Then, the attenuations of the reflected wave signal and the modulated wave signal as a direct signal are adjusted, and after the adjustment, they are combined to form a multipath signal.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a multipath simulator according to an embodiment of the present invention. In addition, the same reference number or symbol is used to represent the same component throughout the drawings.
The multipath simulator shown in the figure first comprises a signal generator 1. The signal generator 1 includes an oscillator 100, an FM modulator 101 connected to the oscillator 100, and the FM modulator 101.
Modulation signal generator 10 for outputting a modulation signal to modulation section 101
Is provided.

Next, the multipath simulator is provided with a phase difference forming means 2. In the phase difference forming means 2, an A / D converter (analog to analog) connected to the modulation signal generator 10 is used.
A digital converter 11 converts the analog modulation signal into a digital signal. The delay means 12 connected to the A / D converter 11 inputs a delay time τ of a reflected wave described later from the outside, delays the input signal by τ time, and outputs the delayed signal. This delay time is in the range of 1 to 40 μs, for example. The adding means 13 connected to the A / D converter 11 inverts the output signal of the delay means 12 and adds it to the output signal of the A / D converter 11. The integrating means 14 connected to the adding means 13 integrates the output of the adding means 13, and the multiplier 15 connected to the integrating means 14 multiplies the output of the integrating means by a constant value to adjust the amplitude of the signal. The multiplier is connected to 15. The adding means 16 adds the phase difference (θ0-θ0 ') of the carrier wave between the direct wave and the reflected wave, which will be described later, to the output of the multiplier 15.

Next, the signal processing of the phase difference forming means 2 will be described. Generally, the instantaneous value θ of the phase of the FM modulated wave is given as follows. θ = θ0 + ∫2πΔf · k (t) dt where θ0: carrier phase Δf: deviation k (t): modulation input waveform (time function).

Therefore, if the phase of the direct wave is θ and the phase of the reflected wave is θ ′, θ = θ0 + ∫2πΔf · k (t) dt θ ′ = θ0 ′ + ∫2πΔf · k (t−τ) dt Becomes The phase difference between these two waves is as follows. θ−θ ′ = θ0−θ0 ′ + ∫2πΔf · {k (t) −k (t−τ)} dt In this equation, the first term represents the phase difference of the carrier and the second term represents the phase difference due to the modulation. .

Therefore, the phase difference forming means 2 implements the processing of the above equation. Returning to FIG. 1,
The multipath simulator comprises a high frequency phase control means 3. The high frequency phase control means 3 includes an amplifier 21 connected to the FM modulator, a 90 ° phase shift means 22 connected to the amplifier 21 for shifting the phase by 90 °, and an output signal of the adding means 16. Phase difference cosine wave forming means 17 for forming a cosine wave using the phase difference, phase difference sine wave forming means 18 for forming a sine wave using the phase difference, phase difference cosine wave forming means 17 and position Phase difference sine wave forming means 18
D to convert each digital signal to analog signal
/ A converter (Digital to Analog Converter) 19 and 2
0, the D / A converter 19 and the 90 ° phase shift means 22
There is provided a mixer 23 for mixing the output signals of, the mixer 24 for mixing the outputs of the D / A converter 20 and the amplifier 21, and an adder 25 for adding the outputs of the mixers 23 and 24. In the phase difference cosine wave forming means 17 and the phase difference sine wave forming means 18, the cosine wave and the sine wave are obtained by a table indexing operation.

Here, the outputs of the mixers 23 and 24 are IR
Letting F and RRF be, IRF = cos (θ−θ ′) RRF = sin (θ−θ ′). Therefore, in the adding means 25, the output is IRF + jIRF = cos (θ−θ ′) + jsin (θ−θ ′) (j: imaginary number). In this way, the high frequency phase difference can be controlled by combining the high frequency modulated wave signal and the phase difference. In the phase difference forming means 2 and the high frequency phase control means 3, the delay device 1
2 to the phase difference sine wave forming means 18 are DSP (Digital
Signal processor). That is, the phase difference is accurately and stably derived by the DSP in the audio frequency range, and the synthesis of the phase difference and the modulated wave signal exceeding the audio frequency is performed by the high frequency phase difference control means 3 which is an analog circuit. Has been realized.

Next, the multipath simulator is connected to the adder 25 and an amplifier 26 for adjusting the attenuation of the reflected wave.
And an amplifier 27 connected to the amplifier 21 for adjusting the attenuation of the direct wave and an adder 28 for combining the outputs of the amplifiers 26 and 27 to form a multipath signal. The attenuation ratios of the direct wave and the reflected wave are input to the amplifiers 26 and 27 from the outside.

According to the present embodiment, in the conventional high frequency delay circuit, the phase characteristic of the crystal filter largely changed with temperature, so that the phase had to be frequently calibrated, but this was improved and the high frequency section was reduced. It also has the advantage of being easy to configure.

[0016]

As described above, according to the present invention, the difference between the modulated signal converted into a digital signal and the delayed modulated signal obtained by delaying this signal by a predetermined time is taken, this difference is integrated, and this integration is performed. The phase difference between the direct wave and the reflected wave from the outside is added to the value to form the phase difference between the direct wave and the reflected wave, and the cosine wave and sine wave signals are formed from the phase difference and these are converted to analog signals. Then, the modulated wave signal and the sine wave analog signal are mixed, the modulated wave signal which is phase-shifted by 90 degrees and the cosine wave analog signal are mixed, and these mixed signals are added to obtain the phase difference and the modulated wave signal. Since the reflected wave signal is formed by synthesizing, the phase difference between the direct wave and the reflected wave is obtained by digital signal processing in the audio frequency range, and thus the temperature stability is significantly improved by deriving the phase difference. thing It made.

[Brief description of drawings]

FIG. 1 is a diagram showing a multipath simulator according to an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional multipath simulator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Signal generator 2 ... Phase difference forming means 3 ... High frequency phase control means

Claims (1)

[Claims] 1. A multipath simulator for simulating and synthesizing a direct wave and a reflected wave, wherein a carrier wave signal is modulated with a modulation signal to form the direct wave and the reflected wave to form a modulated wave signal. The signal generating means (1) takes a difference between the modulated signal converted into a digital signal and a delayed modulated signal obtained by delaying this signal by a predetermined time, integrates the difference, and directly reflects a wave directly from the outside to the integrated value. A phase difference forming means (2) for forming a phase difference by adding a phase difference between a carrier wave and a wave, and forming a cosine wave signal and a sine wave signal from the phase difference and converting these into an analog signal to obtain the modulated wave A signal and the sine wave analog signal are mixed, the modulated wave signal and the cosine wave analog signal that are phase-shifted by 90 degrees are mixed, and these mixed signals are added to obtain the phase difference and the modulated wave signal. Form a reflected wave signal by combining Multipath simulator, characterized in that it comprises a high-frequency phase control means (3) for.